Playwright Tests

Writing Playwright Tests

Tests assert observable behavior from a user's perspective. If a test fails, something is genuinely broken—not timing, not selectors, not environment.

Selector Priority

Use accessible selectors in this order. These query the accessibility tree, making tests resilient to DOM changes.

Never use: CSS classes, nth-child, generated IDs, XPath.

Core Patterns

Waiting

// WRONG - arbitrary timeout
await page.click('#submit');
await page.waitForTimeout(2000);

// CORRECT - web-first assertion auto-retries
await page.getByRole('button', { name: 'Submit' }).click();
await expect(page.getByText('Success')).toBeVisible();

List Counts

// WRONG - .all() doesn't wait
const items = await page.getByRole('listitem').all();
expect(items.length).toBe(5);

// CORRECT
await expect(page.getByRole('listitem')).toHaveCount(5);

Hydration

// Wait for interactivity signal before filling uncontrolled inputs
await expect(page.getByRole('button', { name: 'Add' })).toBeEnabled();
await page.getByPlaceholder('Number').fill('12345');

Optimistic UI (temp ID → real ID)

await page.getByPlaceholder('Number').fill('12345');
await page.getByRole('button', { name: 'Add' }).click();

// Confirm action started
await expect(page.getByPlaceholder('Number')).toHaveValue('');

// Wait for real ID
const newItem = page.locator('a[href^="/item/"]').filter({ hasText: '#12345' });
await expect(async () => {
  const href = await newItem.getAttribute('href');
  expect(href).not.toContain('temp-');
}).toPass({ timeout: 15_000 });

Dialogs

// Set up handler BEFORE triggering
page.once('dialog', dialog => dialog.accept());
await page.getByTitle('Delete').click();

Test Data Isolation

const timestamp = Date.now();
const testName = `Test Item ${timestamp}`;

// Dedicated ID ranges per test file
const getTestId = () => 60_000 + Math.floor(Math.random() * 10_000);

CRUD Verification Workflow

Copy and track:

- [ ] Perform action
- [ ] Wait for save completion
- [ ] Reload page
- [ ] Verify persisted state

await page.getByLabel('Title').fill('New Title');
await page.getByRole('button', { name: 'Save' }).click();
await expect(page.getByText(/unsaved/)).not.toBeVisible({ timeout: 15_000 });

await page.reload();
await page.waitForLoadState('networkidle');
await expect(page.getByLabel('Title')).toHaveValue('New Title');

Timeout Reference

Custom polling:

await expect(async () => {
  const count = await page.getByRole('listitem').count();
  expect(count).toBeGreaterThanOrEqual(5);
}).toPass({ timeout: 10_000, intervals: [100, 250, 500, 1000] });

Configuration

export default defineConfig({
  retries: process.env.CI ? 2 : 1,
  fullyParallel: true,
  workers: process.env.CI ? 1 : 2,
  use: {
    trace: 'on-first-retry',
    screenshot: 'only-on-failure',
    navigationTimeout: 30_000,
  },
});

Debugging Flaky Tests

1. Run with trace: bunx playwright test --trace on
2. View trace: bunx playwright show-trace trace.zip
3. Check for: race conditions, stale selectors, network timing, shared state

Unfixable Tests

test.skip('drag link to topic', async ({ page }) => {
  // TODO: dnd-kit keyboard simulation incompatible with Playwright
  // Manual testing required. Issue: #123
});

Pre-Commit Checklist

- [ ] No waitForTimeout() calls
- [ ] Selectors use getByRole/getByLabel/getByPlaceholder
- [ ] Test data includes timestamp
- [ ] CRUD operations verify persistence after reload
- [ ] Timeouts explicit where needed
- [ ] No shared state between tests
- [ ] Dialog handlers set up before triggering action

Reference

For role options (pressed, checked, expanded, level, etc.) and locator composition (.filter(), scoped .locator()), see:

• Playwright Locators
• Testing Library Guiding Principles